How do i do this physics problem?

[ManBearPig]

I honestly have no fucking idea.

When ultraviolet light with a wavelength of 400 nm falls on a certain metal surface, the maximum kinetic energy of the emitted photoelectrons is 1.10 eV.

What is the maximum kinetic energy K_0 of the photoelectrons when light of wavelength 340 nm falls on the same surface?

Use h = 6.63×10−34 J * s for Planck's constant and c = 3.00×10^8 m/s for the speed of light and express your answer in electron volts.

 

[esun]

Read up, this isn't very hard:

http://en.wikipedia.org/wiki/Photoelectric_effect

 

[SKORPI0]

found the answer here, same exact question.

http://www.cramster.com/physics-answers-5-432906-cpi0.aspx

Response Details:
Energy of photon = Energy needed to remove an electron + Kinetic energy of the emitted electron
Algebraically:

where
h is Planck's constant,

• f is the frequency of the incident photon,
• 
  is the work function (sometimes denoted W instead), the minimum energy required to remove a delocalised electron from the surface of any given metal,

is the maximum kinetic energy of ejected electrons,
f0 is the threshold frequency for the photoelectric effect to occur,
m is the rest mass of the ejected electron, and
vm is the speed of the ejected electron.
Since an emitted electron cannot have negative kinetic energy, the equation implies that if the photon's energy (hf) is less than the work function (&#966, no electron will be emitted.
According to Einstein's special theory of relativity the relation between energy (E) and momentum (p) of a particle is

, where m is the rest mass of the particle and c is the velocity of light in a vacuum.
from the above relation we can solve for maximum kinetic energy .

 

[DrawninwarD]

Read up, this isn't very hard:

http://en.wikipedia.org/wiki/Photoelectric_effect

I've always hated Wikipedia when looking up some physics or calc problems. Wikipedia goes into a ridiculous amount of detail and I'm totally lost by the end of it.

 

[Hacp]

I honestly have no fucking idea.

When ultraviolet light with a wavelength of 400 nm falls on a certain metal surface, the maximum kinetic energy of the emitted photoelectrons is 1.10 eV.

What is the maximum kinetic energy K_0 of the photoelectrons when light of wavelength 340 nm falls on the same surface?

Use h = 6.63×10−34 J * s for Planck's constant and c = 3.00×10^8 m/s for the speed of light and express your answer in electron volts.

This one is really easy to solve if you understand how the photoelectric effect works. You know h and you can solve for frequency.

Frequency=C(speed of light)/wavelength.

Step 1)
Solve for the frequency with 400nm wavelength, then multiply that with h(6.63×10−34 J * s ), then subtract by 1.1eV to get the minimum hf needed for an electron to be excited.
Step 2)
Then solve for frequency at 340nm wavelength, multiply by h, then subtract the minimum hf needed for an electron to be excited, and that is your answer I think.

Remember to convert units. 1 electron volt = 1.60217646E-19 joules
Make sure all your units are in joules or joules*s or 1/s

 

[Hacp]

found the answer here, same exact question.

http://www.cramster.com/physics-answers-5-432906-cpi0.aspx

I don't think you need the kinetic energy formula for this since all the units reduce to joules. I may be wrong though, I am no physics expert.

 

[esun]

I've always hated Wikipedia when looking up some physics or calc problems. Wikipedia goes into a ridiculous amount of detail and I'm totally lost by the end of it.

Part of education is learning how to filter useful information out of a resource. Sometimes you have to read 5 papers on a topic before you figure out the minute detail you needed to know. Though in the case of that Wiki article, the equation needed is spelled out clearly if you just scroll through it.

 

[TecHNooB]

Part of education is learning how to filter useful information out of a resource. Sometimes you have to read 5 papers on a topic before you figure out the minute detail you needed to know. Though in the case of that Wiki article, the equation needed is spelled out clearly if you just scroll through it.

5 papers.. 5 nap periods. I hate sifting through math.